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Theorem un0.1 44054
Description: is the constant true, a tautology (see df-tru 1536). Kleene's "empty conjunction" is logically equivalent to . In a virtual deduction we shall interpret to be the empty wff or the empty collection of virtual hypotheses. in a virtual deduction translated into conventional notation we shall interpret to be Kleene's empty conjunction. If 𝜃 is true given the empty collection of virtual hypotheses and another collection of virtual hypotheses, then it is true given only the other collection of virtual hypotheses. (Contributed by Alan Sare, 23-Apr-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
Hypotheses
Ref Expression
un0.1.1 (      ▶   𝜑   )
un0.1.2 (   𝜓   ▶   𝜒   )
un0.1.3 (   (      ,   𝜓   )   ▶   𝜃   )
Assertion
Ref Expression
un0.1 (   𝜓   ▶   𝜃   )

Proof of Theorem un0.1
StepHypRef Expression
1 un0.1.1 . . . 4 (      ▶   𝜑   )
21in1 43846 . . 3 (⊤ → 𝜑)
3 un0.1.2 . . . 4 (   𝜓   ▶   𝜒   )
43in1 43846 . . 3 (𝜓𝜒)
5 un0.1.3 . . . 4 (   (      ,   𝜓   )   ▶   𝜃   )
65dfvd2ani 43858 . . 3 ((⊤ ∧ 𝜓) → 𝜃)
72, 4, 6uun0.1 44053 . 2 (𝜓𝜃)
87dfvd1ir 43848 1 (   𝜓   ▶   𝜃   )
Colors of variables: wff setvar class
Syntax hints:  wtru 1534  (   wvd1 43844  (   wvhc2 43855
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem depends on definitions:  df-bi 206  df-an 396  df-tru 1536  df-vd1 43845  df-vhc2 43856
This theorem is referenced by:  sspwimpVD  44194
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